I don't think those videos are solid at all and would not recommend putting it to practice based on them. A very educated stance is probably where I'd recommend you start. Balanced, with very good feet coordination.
You definitely should get a qualified trainer to learn this movement. Also, it takes a dedicated learning curve and its best suited for someone with excellent reflexes and timing skills. By all means go for it though!
I agree. I had to start boxing with sparring much more experienced opponents that watched for my welfare but gave me a whooping at the same time. the coach told me to crouch and use the arm and shoulder. after some drills and it comes fairly natural to tuck the shoulder beside the face and right hand up next to my ear or in front of me. its readily there if you need it especially when against the ropes. big advantage if your opponent is all go and you're not up to matching the pace. I would say using shoulder roll doesn't necessarily mean you're fighting like mayweather. Take it back a notch IMO. He has mastered it to a ridiculous;y good standard but plenty of fighters do it like berto, cottocanelo doing it. many fighters do it, just basic thing that comes from a lot of sparring.
greynotsoold is right You're has to be angled of most people try the shoulder roll & are stood too square on, so they're not even really behind they're shoulder If you watch Mayweather & Toney they stand so side on, the right hand side is almost impossible to touch
hardly i have loved boxing for years, just looking for the technical part of the shoulder roll defense thanks to everyone else